[RFC v3 2/8] vfio/type1: Make per-application (VM) PASID quota tunable

Liu, Yi L
2020-01-29T12:07:07Z

From: Liu Yi L <yi.l.liu@intel.com>

The PASID quota is per-application (VM) according to vfio's PASID
management rule. For better flexibility, quota shall be user tunable
. This patch provides a VFIO based user interface for which quota can
be adjusted. However, quota cannot be adjusted downward below the
number of outstanding PASIDs.

This patch only makes the per-VM PASID quota tunable. While for the
way to tune the default PASID quota, it may require a new vfio module
option or other way. This may be another patchset in future.

Previous discussions:
https://patchwork.kernel.org/patch/11209429/

Cc: Kevin Tian <kevin.tian@intel.com>
CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
---
drivers/vfio/vfio_iommu_type1.c | 33 +++++++++++++++++++++++++++++++++
include/uapi/linux/vfio.h | 22 ++++++++++++++++++++++
2 files changed, 55 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index e836d04..1cf75f5 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2243,6 +2243,27 @@ static int vfio_iommu_type1_pasid_free(struct vfio_iommu *iommu,
return ret;
}

+static int vfio_iommu_type1_set_pasid_quota(struct vfio_iommu *iommu,
+ u32 quota)
+{
+ struct vfio_mm *vmm = iommu->vmm;
+ int ret = 0;
+
+ mutex_lock(&iommu->lock);
+ mutex_lock(&vmm->pasid_lock);
+ if (vmm->pasid_count > quota) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ vmm->pasid_quota = quota;
+ ret = quota;
+
+out_unlock:
+ mutex_unlock(&vmm->pasid_lock);
+ mutex_unlock(&iommu->lock);
+ return ret;
+}
+
static long vfio_iommu_type1_ioctl(void *iommu_data,
unsigned int cmd, unsigned long arg)
{
@@ -2389,6 +2410,18 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
default:
return -EINVAL;
}
+ } else if (cmd == VFIO_IOMMU_SET_PASID_QUOTA) {
+ struct vfio_iommu_type1_pasid_quota quota;
+
+ minsz = offsetofend(struct vfio_iommu_type1_pasid_quota,
+ quota);
+
+ if (copy_from_user(&quota, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ if (quota.argsz < minsz)
+ return -EINVAL;
+ return vfio_iommu_type1_set_pasid_quota(iommu, quota.quota);
}

return -ENOTTY;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 298ac80..d4bf415 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -835,6 +835,28 @@ struct vfio_iommu_type1_pasid_request {
*/
#define VFIO_IOMMU_PASID_REQUEST _IO(VFIO_TYPE, VFIO_BASE + 22)

+/**
+ * @quota: the new pasid quota which a userspace application (e.g. VM)
+ * is configured.
+ */
+struct vfio_iommu_type1_pasid_quota {
+ __u32 argsz;
+ __u32 flags;
+ __u32 quota;
+};
+
+/**
+ * VFIO_IOMMU_SET_PASID_QUOTA - _IOW(VFIO_TYPE, VFIO_BASE + 23,
+ * struct vfio_iommu_type1_pasid_quota)
+ *
+ * Availability of this feature depends on PASID support in the device,
+ * its bus, the underlying IOMMU and the CPU architecture. In VFIO, it
+ * is available after VFIO_SET_IOMMU.
+ *
+ * returns: latest quota on success, -errno on failure.
+ */
+#define VFIO_IOMMU_SET_PASID_QUOTA _IO(VFIO_TYPE, VFIO_BASE + 23)
+
/* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */

/*
--
2.7.4